Questions: Voice Leading in Four-Part Writing

Question 1

In a progression, both the soprano and bass move from G up to A simultaneously. Which specific problem does this most likely create?

• A. It creates parallel motion, which is always prohibited in four-part writing
• B. If the voices are a fifth or octave apart on both G and A, it creates parallel perfect intervals that collapse voice independence
• C. The bass should never move upward by step in root-position chords
• D. The soprano and bass must always move in opposite directions regardless of interval size

Answer: (B)

Parallel motion is not inherently prohibited — parallel thirds and sixths are common and effective. The problem is parallel *perfect* intervals (fifths and octaves). If soprano and bass are a fifth apart on G and remain a fifth apart on A, the voices fuse acoustically and lose independence. The prohibition is specifically about perfect consonances that make voices sound like one. Contrary motion between outer voices is preferred precisely because it avoids this fusion.

Question 2

A student must write a large leap upward (a major sixth) in the alto voice. According to standard voice-leading practice, what should happen immediately after the leap?

• A. The alto should continue ascending to maintain melodic momentum
• B. The alto should leap back down by the same interval to balance the gesture
• C. The alto should resolve stepwise downward, back toward the direction it came from
• D. Large leaps are prohibited in inner voices and should be avoided entirely

Answer: (C)

A large leap creates tension that wants resolution by stepwise motion in the opposite direction. A large leap upward wants to be followed by stepwise descent; a large leap downward wants stepwise ascent. This is not an absolute rule but a strong tendency — the leap 'stretches' the voice's melodic line and the subsequent step releases the tension. Large leaps in inner voices are not prohibited; they just require careful preparation and resolution.

Question 3

The soprano-bass relationship carries primary structural importance in four-part writing — it functions as the outer frame within which the inner voices operate.

• T. True
• F. False

Answer: True

The outer voices (soprano and bass) define the harmonic boundaries of the texture. When soprano and bass move in contrary motion, the texture opens and closes in a way that sounds structurally balanced. The alto and tenor fill the interior, completing the harmony and connecting smoothly between outer-voice events. Analyzing four-part writing begins with the soprano-bass framework.

Question 4

Parallel thirds between the soprano and bass are prohibited in four-part writing for the same reason parallel fifths are — they collapse voice independence.

• T. True
• F. False

Answer: False

Only parallel *perfect* intervals are prohibited — unisons, fifths, and octaves. These intervals create acoustic fusion that makes independent voices sound like one. Parallel thirds and sixths are imperfect consonances that sound harmonically full while maintaining distinct voice identity. They are not only permitted but common and desirable, particularly between inner voices or between soprano and tenor.

Question 5

Why are parallel fifths and parallel octaves prohibited in four-part writing, while parallel thirds and sixths are acceptable?

Model answer: Perfect intervals (fifths and octaves) have a simple frequency ratio that causes voices to acoustically fuse — they sound like a single voice rather than two independent lines. This collapses the texture from four voices to fewer. Parallel thirds and sixths are imperfect consonances with more complex ratios; they blend harmonically but maintain distinct timbral identities, preserving the sense of independent voices. The prohibition exists to keep all four lines audibly separate and structurally distinct.

This connects to acoustics: perfect intervals appear prominently in the harmonic series together, making doubled voices hard to distinguish. The rule is not arbitrary convention but an observation about how acoustic fusion undermines the compositional goal of voice independence.